Closure cap with injection molded annular gasket and method of making same

ABSTRACT

A closure cap and method of making the same wherein an annular or ring-shaped gasket is injection molded onto the inner surface of a cap shell formed of plastic or metal. The annular or ring-shaped gasket includes radially extending tabs integrally formed therewith, one of said tabs being formed at a location wherein the plastic melt is fed to an annular gasket-forming channel in a mold core and another of said tabs being formed at the location wherein plastic melt is discharged from said channel. Preferably, said other tab includes a cold well formation which communicates with the annular gasket through a connecting portion of reduced cross-sectional area with respect to the cross-sectional areas of both the gasket and the cold well formation.

BACKGROUND OF THE INVENTION

The present invention generally relates to new and useful improvementsin closure caps for glass and plastic containers and, more particularly,to a closure cap having an improved injection molded annular gasket andmethod of making the same. In this regard, an important aspect of thepresent invention is directed to a closure cap having a one-piece orunitary cap shell formed of a polyolefin such as, for example,polypropylene, in which an annular or ring-shaped gasket characterizedby improved uniformity, definition and consistency which is composed ofa moldable resin such as, for example, a thermoplastic elastomer, isinjection molded onto the inner surface of the closure cap shell via aninsert molding procedure.

Closure caps having full disks formed by compression or injectionmolding the same in a closure shell are known. For example, U.S. Pat.No. 4,398,874 describes a molding tool for forming a full disk liner ina closure shell which includes a central punch or molding member and ashell positioning sleeve disposed externally of the molding member thatis received within a cap shell. Liner material deposited within theshell is contacted by the punch and forms a full disk liner with the capshell. Correspondingly, U.S. Pat. No. 4,803,031 describes a closure capand method wherein an injection molded full disk gasket is formedfollowed by injection molding the closure cap shell around the thusformed gasket. These full disk closure caps while providing generallysatisfactory sealing on containers are characterized by highermanufacturing costs associated with using greater amounts ofgasket-forming resin and also by the disadvantages of having the entireinside surface of the cap shell fully covered thereby increasing thepossible migration of gasket components into product (particularly foodproducts) in the container sealed therewith and also making the innersurface of the cap shell unavailable for displaying labels or othermessage-conveying indicia.

U.S. Pat. No. 5,685,443 describes a composite closure cap where anannular gasket providing a top and side seal is injection molded onto ametal disk followed by injection molding a plastic skirt around the diskin surrounding and capturing relation therewith. This composite closurewhile utilizing an injection molded annular gasket requires the presenceof a separate disk which adds to the cost of the closure and to thecomplexity of manufacturing the same.

SUMMARY OF THE INVENTION

present invention overcomes the foregoing disadvantages of these priorart closures by providing a novel closure utilizing a plastic or metalcap shell and an injection molded annular or ring-shaped gasket whereinthe central portion of the inner surface of the cap shell is free ofgasket material.

In accordance with an important aspect of the present invention, animproved closure cap is provided which includes a unitary or one-pieceplastic or metal shell and an annular ring-shaped gasket having inwardlyradially extending tabs integrally formed therewith, one of said tabsbeing formed at the location wherein plastic melt is fed to an annulargasket-forming channel in a mold core and the other of said tabs beingformed at the location wherein plastic melt is discharged from saidchannel. The latter of said tabs, in accordance with a preferredembodiment of the present invention, includes a cold well whichcommunicates with the annular gasket forming channel through apassageway of reduced cross-sectional area with respect to thecross-sectional areas of both the gasket forming channel and the coldwell.

It is, therefore, an object of the present invention to provide animproved closure cap having a novel injection molded annular gasket andmethod of making the same.

Another object of the present invention is to provide a closure caphaving a one-piece plastic or metal shell and an injection molded topseal annular gasket which utilizes a cost-effective amount of moldable,gasket-forming material and which provides an efficient seal with theend finish of a container to which the closure cap is applied.

Another object of the present invention is to provide an injectionmolded annular gasket formed by insert molding the same in a one-piececlosure cap shell wherein the uniformity and consistency of the gasketis enhanced which gasket is characterized by integral radially extendingtabs at locations along the periphery of the gasket corresponding to thelocations wherein the melt is supplied to and from a gasket definingchannel.

These and other objects of the present invention will be apparent fromthe following detailed description taken in conjunction with theaccompanying drawings wherein like reference numerals refer to likeparts and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially broken away, of a closure capembodying the present invention and a portion of a container on whichthe closure is fitted;

FIG. 2 is a bottom plan view of the closure cap shown in FIG. 1;

FIG. 3 is a sectional view of the closure cap shown in FIGS. 1 and 2taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional view of the closure cap shown in FIGS. 1 and 2taken along the line 4-4 of FIG. 2;

FIG. 5 is a schematic side elevation view of a mold apparatus which canbe used to manufacture the closure cap of the present invention;

FIG. 6 is a schematic perspective view of a portion of the moving platenof the mold apparatus shown in FIG. 5 which is separated from a coreplate of the stationary platen;

FIG. 7 is a schematic perspective view of the moving platen of the boldapparatus of the present invention with the stripper plate thereofremoved;

FIG. 8 is a partial top plan view of the mold core of the presentinvention;

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8;

FIG. 10 is a schematic sectional view of the core head of the moldapparatus shown in FIGS. 8 and 9;

FIG. 11 is an enlarged sectional view of the melt discharge side of thecore head shown in FIG. 10;

FIG. 12 is an enlarged sectional view of the melt inlet side of the corehead shown in FIG. 10;

FIG. 13 is a fragmentary perspective view, partially broken away, of theclosure cap of another embodiment of the present invention and a portionof a container on which the closure cap is fitted; and,

FIGS. 14-18 are schematic views of a mold apparatus for manufacturingthe closure cap shown in FIG. 13 with each of the views showingsuccessive phases of the closure shell manufacturing process.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and with particular reference to FIGS. 1-4, aclosure cap embodying the present invention is generally designated bythe reference numeral 20. As shown, closure cap 20 is applied to acontainer 21 and includes an end panel 22 having an inner or bottomsurface 23, a skirt 24 which terminates in an enlarged axially extendingcylindrical section 25.

As best shown in FIGS. 1, 3 and 4, bottom cylindrical section 25 is, inthe illustrated embodiment, connected to a tamper indicating band 26 bya plurality of frangible bridges which includes an upper band portion 27and a lower band portion 28 which are connected by a flexible hinge 29.Closure cap 20 is provided with a spiral thread 31 on the interiorsurface of skirt 24, however, it will be appreciated that othercontainer-engaging securement systems such as, for example, conventionallugs and the like may be used without departing from the presentinvention. Correspondingly, the closure cap can be made with other formsof tamper indicating bands or, if desired, without any such band.

In accordance with an important aspect of the present invention, closurecap 20 includes an injection molded annular or ring-shaped gasket 32positioned around the outer periphery of the inner or bottom surface 23for top-seal engagement with an end finish or top edge 33 of container21 which defines an open mouth 34 of the container. As shown in FIG. 1,container 21 includes a spiral thread 35 sized to matingly engage thread31 on closure cap 20 and also includes a retainer bead 36 for engagementwith the bottom edge of lower tamper indicating band portion 26 in amanner which is well known in the art.

Annular or ring-shaped injection molded gasket 32 is provided with anintegral radially inwardly extending tab 37 corresponding to thelocation at which inlet melt feed is supplied to the mold cavity duringthe injection molding process and a cold well tab 38 and connectorportion 39 which also are integral with the gasket 32 and whichcorrespond to the location at which melt is discharged from the moldcavity defining the gasket. The precise manner in which these respectivetabs are formed will be more fully described in connection with the moldapparatus.

In accordance with another aspect of the described embodiment of thepresent invention, the top surface 40 of gasket 32 is provided with aplurality of V-shaped ribs that provide improved seal-forming contactwith the closure finish. It is important to note that the formation ofthese V-shaped ribs via injection molding gives them significantlybetter definition than that attainable by other manufacturingprocedures, such as, for example, compression molding. In this regard,however, it will be appreciated that, if desired, the top surface 40 ofgasket 32 can be flat or of other configurations.

Closure cap 20, in accordance with the present invention, is made ofsuitable moldable polyolefin such as, for example, polypropylene andhomopolymers and copolymers thereof. In this regard, however, it will beappreciated that other suitable moldable plastic resins may be used informing the closure cap. Alternatively, if desired, the injection moldedannular gasket of the present invention may also be incorporated inmetal closures.

Annular or ring-shaped gasket 32 may likewise be formed of any resilientor elastomeric materials which provide the desired seal with a containerfinish, however, vinyl chloride-free resins or non-PVC materials arepreferred. If desired, suitable additives such as those providingimproved oxygen barrier and/or oxygen scavenger properties, as well asthose which facilitate torque release may be incorporated into thegasket composition.

These non-PVC materials include rubbery block copolymers dispersed in amatrix of polyolefin as the continuous phase, with a moldablethermoplastic elastomer being especially preferred since they possess anumber of processing advantages. Gasket compositions which can beeffectively used include those composed of a thermoplastic elastomericmaterial selected from a moldable-saturated ABA-type block copolymerbased on styrene and butadiene such as styrene-ethylene-butylene styrene(SEBS) type block copolymers containing from about 20% to about 40%styrene and about 60% to 80% ethylene-butylene co-monomers such asKraton® G-2705, available from Shell Chemical Corporation. Preferredthermoplastic elastomers also include the EPDM(ethylene-propylene-dicyclopentadiene) elastomers such as thosecommercially available under the trade name Santropene® from MonsantoCompany. Other suitable thermoplastic elastomers are those which areavailable from Advanced Elastomer Systems, L. P. of Akron, Ohio.

A suitable apparatus for manufacture of the closures of the presentinvention is generally depicted in FIGS. 5-12. FIGS. 5-9 schematicallydepict a mold apparatus having a feed system for supplying preformedclosure cap shells to the molding station wherein the injection moldedgasket is formed via insert molding procedures. It will be appreciatedthat while a specific transport mechanism is described herein forsupplying closure cap shells to the mold apparatus and fortransportation of such closure caps through and from that apparatus,other transport feeding systems such as, for example, belt and/orrobotic closure cap transportation arrangements, could be used ifdesired. A common feature of all molding systems which is important tothe present invention, however, concerns the precise insert moldingarrangement by which annular or ring-shaped gaskets are formed withexceptional preciseness in their configuration and without airentrapment.

As generally shown in FIG. 5, the molding apparatus includes a movingplaten 45, and a stationary platen 46 which comprises a core section 47.Moving platen 45 includes a transfer drive 48, a transfer dial 49, astripper plate 50 and feed chute 51 which will be more fully describedin conjunction with FIGS. 6 and 7. Correspondingly, the core section 47schematically shown in FIG. 5 includes individual mold cores 52 and 53.Melt is supplied to the core section 47 from an injection unit 54 whichfeeds melt to a manifold section 56 that, in turn, supplies pressurizedmelt feed via line 57 and 58.

As best shown in FIG. 7, moving platen 45 includes a rotatable starwheel transfer mechanism generally depicted by the reference numeral 60which has ten cap-receiving pockets, each of which is generallydesignated by the reference numeral 61. As shown, caps are supplied fromfeed chute 51 into each of the individual pockets 61 until the starwheel is fully loaded. Individual mold cores on mold core section 47 arerespectively received within each of the cap shells. After thegasket-forming operation is completed, the mold is opened and thecompleted closure caps discharge from the moving platen via dischargechute 63. If desired, pressurized air may be used to facilitate loadingand removal of the cap shells in the star wheel transfer mechanism. Inthis regard, it will be appreciated that the number of cap-receivingpockets located in the star wheel can be varied. For example, in thearrangement illustratively depicted in FIG. 7, ten cap-receiving pocketsare shown, while eight such pockets are shown in FIG. 6.

Referring to FIG. 6, it will be observed that a core plate 64 isdepicted in space-away relationship to the moving platen 46. As will beapparent from the description of FIGS. 8 and 9, the portion of coreplate 64 facing moving platen 45 includes a plurality of standoff posts(shown in FIG. 8 and designated by reference numeral 65) which controlthe depth of penetration of the individual mold cores into each of theclosure cap shells.

Referring now to FIGS. 8-12, each of the mold cores (designated byreference numeral 52) is sized to be received within the closure capshell for direct contact with the inner or bottom surface 23 of endpanel 22 of a given closure cap. Melt supplied from manifold 56 and meltfeed line 57 is discharged through a gate 66 into an inlet melt feedline 68 and from there into an annular channel 67 which, together withthe inner or bottom surface 23 of the closure cap forms agasket-defining mold cavity. Typically, with plastic enclosure capshells, the mold cores will penetrate the end panel surface to a limitedand controlled extent, while with metal closure cap shells no suchpenetration is needed in order to achieve effective melt flow shut-offfor containment of the melt within the gasket-defining mold cavity. Themelt flow from inlet 68 passes in clockwise and counterclockwisedirections through the annular channel 67 and is discharged into a coldwell portion 73 of the core via a connecting passage 74. In accordanceof an important aspect of the present invention, the connecting passage74 has a reduced cross-sectional configuration to ensure that themeeting melt streams will knit at that location and, additionally,eliminates or at least greatly minimize the trapping of any air in thegasket itself. This reduced size passageway results in a lower pressureon the inside portion of the cold well than is present in the annulargasket-defining portion 67 causing any air present in the melt to bereadily discharged into the cold well.

As shown, a vent line 71 can be provided to draw a vacuum on the systemto further facilitate air removal during the feed of melt. Also, asshown, an air line 72 can be provided to facilitate removal of thefinished closure after the injection molding of the gasket has beenaccomplished and the mold opened. If desired, vent line 71 and air line72 can be coupled to further facilitate removal of the finished closurewhen the molding operation is complete.

Heat built up during the injection molding process can be dissipatedthrough the use of water cooling, which can be accomplished by an outletwater line 70 which is in flow communication with an inlet water line(not shown).

As best shown in FIGS. 11 and 12, the bottom surface 75 of annularchannel 67 is provided with a plurality of V-shaped grooves which form aplurality of concentric V-shaped ribs that impart improve seal-formingcontact with the closure finish. As previously noted, the formation ofthese V-shaped ribs by injection molding process gives themsignificantly better definition than is achievable by other moldingprocedures.

FIG. 13 generally designates a further embodiment of the presentinvention in the form of a modified closure cap 80 having a layer ofmetallic foil or other suitable material bonded to the inner surface 23of end panel 22 and to which the annular or ring-shaped injection moldedgasket is bonded. This construction is particularly suitable forapplications wherein improved oxygen barrier properties are requiredand/or where it is desirable to provide a visible display on theinterior of the closure cap. As such, the annular injection moldedgasket is particularly suitable for such applications, since it leavesthe central portion of the panel exposed, enabling use of such area forthe display of printed matter and the like.

FIGS. 14-18 illustrate one procedure for manufacturing this closureshell. As shown in FIG. 14, a mold apparatus is provided which includesan upper mold component 83 having a melt feed line 84 and gate 85, alower mold component 86 and a core 87. A sheet or strip of foil or othersuitable material which is to be laminated to the interior surface 23 ofthe closure cap shell is positioned between upper and lower moldcomponents 83, 86. As shown in FIG. 15, these mold components areclosed, thereby trapping and securely holding the strip 82 in place.

Core 87 is then positioned within lower mold component 86 in directcontact with the strip 82 and defines a mold cavity 88 which correspondsto the configuration of the closure cap to be formed therewith. A supplyof melt 89 is then fed into the cavity which, as shown in FIG. 17, formsclosure portion 90 and, at the same time, due to the high pressure ofthe melt feed, breaks the marginal portions of the foil strip andcontinues to flow as shown in FIG. 18 to form the finished closureshell. The mold portions are then opened and the formed closure capshell removed therefrom.

While the present invention has been described in connection with thecontext of various embodiments, it will be apparent to those skilled inthis art that modifications and variations may be made therefrom withoutdeparting from the sprit and scope of this invention. Accordingly, thisinvention is to be construed and limited only by the scope of theappended claims.

1-38. (canceled)
 39. A closure cap comprising: a shell which includes anend panel and an integral skirt downwardly extending therefrom, said endpanel having a generally circular inside surface of a given outerdiameter; and, an injection molded annular gasket, said annual gaskethaving a ring-shaped body which includes an outer edge and an inneredge, said outer edge having a diameter which is less than the outerdiameter of said end panel inner surface whereby said outer edge of saidgasket body is inwardly spaced from the outer periphery of said endpanel inside surface to define a substantially gasket-free annularborder which surrounds said ring-shaped gasket body, said gasket havinga width sufficient to provide a top seal with an end finish of acontainer mouth to which said closure is applied, said inner edge ofsaid ring-shaped gasket body surrounding a generally gasket-freeinterior portion of said inside surface of said end panel, said gasketalso including at least one inwardly extending tab integrally formedtherewith, said inwardly extending tab including an inner-most and anouter-most portion, said inner-most portion having a relatively largecross section with respect to the cross section of said outer-mostportion.
 40. The closure of claim 39 wherein said tab extends radiallyinwardly from the inner edge of said ring-shaped gasket body.
 41. Theclosure cap of claim 39 wherein said ring-shaped gasket body includes atop seal-forming surface defined by a plurality of concentric ribs. 42.The closure cap of claim 41 wherein said concentric ribs are conicallyshaped.
 43. The closure cap of claim 39 wherein said gasket is composedof a moldable resin which is substantially free of vinyl chloride. 44.The closure cap of claim 39 wherein said gasket is composed of athermoplastic elastomer.
 45. The closure cap of claim 39 wherein saidshell is formed of a moldable thermoplastic resin.
 46. The closure capof claim 45 wherein said thermoplastic resin is a polyolefin.
 47. Theclosure cap of claim 45 wherein said thermoplastic resin ispolypropylene.
 48. The closure cap of claim 45 wherein said end panel ofsaid shell includes a layer of an oxygen barrier film.
 49. The closurecap of claim 48 wherein said layer of oxygen barrier film is adhered tothe inside face of said end panel.
 50. The closure cap of claim 39wherein said shell is composed of a metal.
 51. A closure cap comprising:a shell which includes an end panel and an integral skirt downwardlyextending therefrom, said end panel having a generally circular insidesurface of a given outer diameter; and, an injection molded annulargasket formed directly on the end panel to define a unitary, integralshell and gasket arrangement, said annual gasket having a ring-shapedbody which includes an outer edge and an inner edge, said outer edgehaving a diameter which is less than the outer diameter of said endpanel inner surface whereby said outer edge of said gasket body isinwardly spaced from the outer periphery of said end panel insidesurface to define a substantially gasket-free annular border whichsurrounds said ring-shaped gasket body, said gasket having a widthsufficient to provide a top seal with an end finish of a container mouthto which said closure is applied, said inner edge of said ring-shapedgasket body surrounding a generally gasket-free interior portion of saidinside surface of said end panel, said gasket also including at leastone inwardly extending tab integrally formed therewith, said inwardlyextending tab including an inner-most and an outer-most portion, saidinner-most portion having a relatively large cross section with respectto the cross section of said outer-most portion.
 52. The closure ofclaim 51 wherein said tab extends radially inwardly from the inner edgeof said ring-shaped gasket body.
 53. The closure cap of claim 51 whereinsaid ring-shaped gasket body includes a top seal-forming surface definedby a plurality of concentric ribs.
 54. The closure cap of claim 53wherein said concentric ribs are conically shaped.
 55. The closure capof claim 51 wherein said gasket is composed of a moldable resin which issubstantially free of vinyl chloride.
 56. The closure cap of claim 51wherein said gasket is composed of a thermoplastic elastomer.
 57. Theclosure cap of claim 51 wherein said shell is formed of a moldablethermoplastic resin.
 58. The closure cap of claim 57 wherein saidthermoplastic resin is a polyolefin.
 59. The closure cap of claim 57wherein said thermoplastic resin is polypropylene.
 60. The closure capof claim 51 wherein said end panel of said shell includes a layer of anoxygen barrier film.
 61. The closure cap of claim 60 wherein said layerof oxygen barrier film is adhered to the inside face of said end panel.62. The closure cap of claim 51 wherein said shell is composed of metal.63. A closure cap comprising: a shell which includes an end panel and anintegral skirt downwardly extending therefrom, said end panel having acontinuous planar inside surface; and, an injection molded annulargasket formed by insert molding on said end panel, said annual gaskethaving a ring-shaped body which includes an outer edge and an inneredge, said gasket having a width sufficient to provide a top seal withan end finish of a container mouth to which said closure is applied,said inner edge of said ring-shaped gasket body surrounding a generallygasket-free interior portion of said inside surface of said end panel,said gasket also including at least one inwardly extending tabintegrally formed therewith, said inwardly extending tab including aninner-most and an outer-most portion, said inner-most portion having arelatively large cross section with respect to the cross section of saidouter-most portion.
 64. The closure of claim 63 wherein said tab extendsradially inwardly from the inner edge of said ring-shaped gasket body.65. The closure cap of claim 63 wherein said ring-shaped gasket bodyincludes a top seal-forming surface defined by a plurality of concentricribs.
 66. The closure cap of claim 65 wherein said concentric ribs areconically shaped.
 67. The closure cap of claim 63 wherein said gasket iscomposed of a moldable resin which is substantially free of vinylchloride.
 68. The closure cap of claim 63 wherein said gasket iscomposed of a thermoplastic elastomer.